Protective mechanical ventilation in patients with risk factors for ARDS: prospective cohort study

OBJECTIVE: To evaluate the association that protective mechanical ventilation (MV), based on V(T) and maximum distending pressure (MDP), has with mortality in patients at risk for ARDS. METHODS: This was a prospective cohort study conducted in an ICU and including 116 patients on MV who had at least one risk factor for the development of ARDS. Ventilatory parameters were collected twice a day for seven days, and patients were divided into two groups (protective MV and nonprotective MV) based on the MDP (difference between maximum airway pressure and PEEP) or V(T). The outcome measures were 28-day mortality, ICU mortality, and in-hospital mortality. The risk factors associated with the adoption of nonprotective MV were also assessed. RESULTS: Nonprotective MV based on V(T) and MDP was applied in 49 (42.2%) and 38 (32.8%) of the patients, respectively. Multivariate Cox regression showed that protective MV based on MDP was associated with lower in-hospital mortality (hazard ratio = 0.37; 95% CI: 0.19-0.73) and lower ICU mortality (hazard ratio = 0.40; 95% CI: 0.19-0.85), after adjustment for age, Simplified Acute Physiology Score 3, and vasopressor use, as well as the baseline values for PaO(2)/FiO(2) ratio, PEEP, pH, and PaCO(2). These associations were not observed when nonprotective MV was based on the V(T). CONCLUSIONS: The MDP seems to be a useful tool, better than V(T), for adjusting MV in patients at risk for ARDS.